1. Field of the Invention
This invention relates to improving the physical and bacteriological properties of cotton and cellulose-containing textiles. More specifically this invention relates to the products and the process of imparting a plurality of improvements to cellulosic textiles by chemical means, and heat treatment.
2. Description of the Prior Art
It is well known to impart durable wrinkle resistance to cellulosic fabrics such as cotton by impregnation with an aqueous solution of a suitable thermosetting resinuous precondensate or cellulose crosslinking agent, usually with an appropriate catalyst, and eventually curing of the impregnated fabric. Such treatments have been effective in improving the wrinkle resistance and the shape holding properties of cotton fabrics and have resulted in greatly increased demand for "easy-care," "wash-and-wear," and "permanent-press" cotton fabrics because they combine traditional comfort, washability, and economy of native fibers with easy care properties that are desired in todays textile market.
A variety of processes has been developed and used for improving wrinkle resistance or recovery of fabrics and garments. These processes are known in general as pad-dry-cure resin treatments, where one or more resins are applied to the fabrics through padding, and the fabrics are partially dried before the resin is cured.
The conventional thermosetting resin systems, either post cured and precured, result in embrittlement and reduction of mobility of the cellulosic fibers to such an extent that tearing strength, breaking strength and abrasion resistance are seriously impaired. Tear strength is often reduced by 50%, breaking strength by 50-60%, and abrasion resistance by 75-85%.
Over the last several years, considerable research has been conducted to find ways of overcoming this problem without compromising the wash-wear or durable-press performance of the fabric. Many variations from the pad-dry-cure process have been developed in attempts to solve the problem. These include processes involving a multi-stage padding and curing, processes involving a pad and wet-fixation prior to cure, and processes involving polymeric additives. The results achieved through all of these processes have been marginal, and the processes have often been found to be cumbersome and expensive.
A particular and promising approach to the production of easy-care, durable-press fabrics has involved the wet fixation of resin-forming crease-proofing agents such as formaldehyde-melamine precondensates, as disclosed in Textile Research Journal 37, 70 (1967) and in U.S. Pat. No. 3,138,802. In this type of process, the fiber system such as a cotton fabric is protected against an excessive strength loss by fixation of a suitable resin forming and creasing proofing agent within the fibers while they are wet and swollen. In the laboratory process, the fabric, padded with the solution of the reagents at a pH of 2, is heated in a moist atmosphere to achieve fixation of the N-methylol reagents. Part of the resin contact is firmly fixed in the cotton fibers and the fabric at this stage; after rinsing and introduction of catalyst and softener, the fabric can be cured immediately or stored prior to cure at elevated temperature. Wet fixation processes have generally been cumbersome, or have required special equipment and processing.
The use of nonreactive or coreactive additives for the purpose of obtaining improved abrasion resistance in durable-press fabrics is discussed in Textile Research Journal 37, 253 (1967). This type of approach is exemplified in U.S. Pat. No. 3,877,872 which calls for the inclusion of tetraethylene glycol dimethyl ether in a conventional reagent bath consisting of methylated methylolmelamine and a crosslinking agent, such as dimethyloldihydroxyethyleneurea, and a catalyst such as zinc nitrate or magnesium chloride. This same patent illustrates, also, the introduction of an aqueous emulsion of polyurethane to fabric in a separate step to develop a fiber coating that enhances abrasion resistance. In general, the benefits are less than desired from such modifications of conventional crosslinking treatments.
In U.S. Pat. No. 3,306,992 there is described a method for treating cotton-containing fabric for obtaining improved wrinkle-resistance and improved abrasion resistance which involves padding the fabric through a resin finishing bath containing a mixture of a conventional thermosetting resin in combination with a latex emulsion prior to a subsequent drying step, and a final curing at elevated temperature. In this case the additive is a synthetic rubber latex, which consists of a carboxy-modified butadiene-styrene copolymer in emulsion form. This preformed polymer undergoes some reaction with the resin-forming reagent to produce a coating on fabric, yarn, and fiber surfaces.
U.S. Pat. No. 3,311,496 describes a process that involves pretreatment of fabric with hardenable aminoplasts by the wet steam process before treatment with a creaseproofing hardenable aminoplast. At a given level of wrinkle recovery, the tensile strength of the product is significantly higher than that of the unpretreated fabric. U.S. Pat. No. 2,992,138 teaches to overcome adverse effects upon tensile strength of fabric caused by zinc nitrate catalyst employed with dimethylolethyleneurea by introducing an alkali metal acetate into the reagent mixture. U.S. Pat. No. 3,402,988 achieves improved abrasion resistance and other properties by first impregnating fabric with conventional wash-wear formulations and second applying a catalyst deactivator on the top and bottom of the fabric, so that superior properties are retained in the surface areas. According to U.S. Pat. No. 3,634,019 high strength losses in cellulosic fabrics when treated with creaseproofing agents to produce durable-press properties are avoided by eliminating a major part of the usual acidic catalyst and adding an amount of zinc or aluminum acetate. In U.S. Pat. No. 3,807,952, there is a method described for improving abrasion resistance in crosslinked cellulosic fibers which amounts to introducing salt additives to the conventional reagent system. U.S. Pat. No. 3,827,994 refers to imparting abrasion resistance and permanent press properties to cellulosic materials by employing N-methylol-lactamide in conjunction with other conventional N-methylol reagents. U.S. Pat. No. 3,526,474 describes a process for imparting abrasion resistance and wrinkle resistance and durable-press properties to cellulosic fibers by first applying the N-methylol reagent and subjecting it to curing conditions in the presence of a so-called polymerization catalyst and later impregnating the treated fabric with an acid latent catalyst, drying and finally curing. U.S. Pat. No. 3,656,885 achieves improvement in wear resistance of cotton fabrics in wash-wear or durable-press garments by sequential separate steps of swelling, substitution, and crosslinking of fabric and, more specifically, by applying to cotton pairs of monofunctional and polyfunctional reactive swelling agents.
In the above-cited prior art and in conventional processes for development of easy-care or durable-press properties in cotton fabrics, the N-methylol resins reduce the hydrophilic characteristics of the original cotton fiber, and this is further accentuated and aggravated by the introduction of supplementary additives. The results is that the hydrophilic characteristics of the cotton are further reduced. Since the cotton fiber is unique among major textile fibers for apparel in its hydrophilic characteristics, it is undesirable that these be lost; in general, reduction in the hydrophilic characteristics of cotton results in decreased comfort to a wearer and decreased soil removal during laundering. The removal of oily soil constitutes a special problem for durable-press cotton fabrics and an even greater problem for durable-press cotton/polyester fabrics.
There is an increasing need for inhibition of microbiological growths on fabric for several reasons, including the reduction in persistence of virus on fabric, reduced transmission of infection by means of fabric, reduction or prevention of perspiration odor on fabrics, for which Staphylococcus aureus and Stephylococcus epidermidis are primary contributors (R. W. Sidwell, G. J. Dixon, and E. McNeil, Applied Microbiology 14, 55 (1966); E. McNeil, J. M. Blanford, E. A. Choper, et al., American Dyestuff Reporter 52, P1010 (1963); P. J. Radford, American Dyestuff Reporter 62 (11) 48 (1973); T. L. Vigo, G. F. Danna, and C. M. Welch, Carbohydrate Research 44, 45 (1975). Some fundamentals of antibacterial finishing have been discussed by Gagliardi (American Dyestuff Reporter 51, P49 (1962) and Radford (see above) and some finishes for fabric have been described by Gagliardi, by McNeil et al., by Radford, and by Vigo et al. (foregoing references). Gagliardi (above ref.) described a variety of types of finishes for antibacterial activity, most of which (excepting those finishes containing mercury, tin, and silver) showed little activity remaining after 10 launderings and none of which combined antibacterial activity with other desirable properties, such as muss resistance and easy-care, oily soil release, or high retentions of strength and abrasion resistance.